Protein quality control entails the removal of misfolded proteins. Accumulation of such misfits leads to activation of the unfolded protein response (UPR) with eventual pathological consequences to the cell and organism, should misfolded proteins persist. Proteins, either luminal or membrane-disposed, that fail to fold in the ER are often retro-translocated or 'dislocated' into the cytosol for degradation. This dislocation is to a large extent ubiquitin- dependent, as is the degradation of misfolded cytosolic proteins. The overall goal of the project is to study the mechanism of ER associated degradation (ERAD) and how disruption of this process leads to, or is an important factor in, the development of various protein misfolding diseases. To achieve this goal, novel catch-and-release probes will be applied in combination with photo-crosslinkers to identify new components involved in dislocation: in vivo ubiquitin acceptors of the ERAD ubiquitinating conjugating enzyme Ubc6e and in vivo interaction partners of Ubc6e. It is currently difficult to extend the study of ER stress control to the organismal level. The Ploegh lab has developed tools that now allow us to block the ER dislocation process in a non-toxic manner, an approach that will be exploited and extended to two new in vivo mouse models. Identification of novel dislocation components will be an important extension of our basic knowledge of ERAD machinery. Because many diseases have been attributed to the accumulation of misfolded proteins, the proposed experiments are relevant to numerous diseases.